Ingot mold and stool assembly



S p 1936- E. GATHMANN INGOT MOLD AND STOOL ASSEMBLY Filed Dec. 5, 1955Patented Sept; 15, 1936 V UNITED STATES PATENT OFFICE v 2,054,591 moormom) ANDSTOOL assmmm Emil Gathmann, Baltimore, Md. Application December3, 1935, Serial No. 52,709

Claims. 01. 22-139) 7 This invention relates ingot 'mold and stoolassemblies and more particularly to such assemblies in which the moldproper is of the class known in the art as the big-endp mold, open attop and bottom. I

The soundest, best quality commercial steel products are made from fullydeo xidized or killed steel ingots cast in big-end-up molds. Oneimportant factor in obtaining the best resuits in big-end-up killedsteel ingot practice is the extracting of the heat of the ingot metalmore rapidly from the bottom portion of the ingot than from the top partthereof.

An object of my invention is to provide a biglo end-up mold and stoolassembly that particularly favors the extraction of heat from theextreme bottom portion of an ingot cast within the mold so as to producea high differential cooling rate between the bottom surface and thevertical 'or m side, surfaces of the ingot, and which consequentlyproduces an improved ingot and ultimate product.

A further object is to provide an assembly of- 30 following description,the appended claims, and,

the accompanying drawing, in which:

Figure 1 is a central, vertical sectional view of a mold and stoolassembly embodying the invention;

35 Figure 2 is a horizontal section in a plane indicated by the line 2-2of Figure 1; and

Figure .3 is a central vertical sectionalview of a modified assembly,only the lower part of the mold being shown.

40 In accordance with my invention, I preferably employ a big-end-upmold having a large bottom opening, one form of mold adapted for use inassemblies embodying the invention being shown at M in Figures 1 and 2as restingdirectly upon 45 and being supported by a stool S. The mold Mcomprises generally vertical walls I defining a mold matrix 2 open atits top and bottom ends,

the bottom opening 3 being of substantial extent.

As shown, the mold is provided with lifting lugs 50 l of a known kind,and the stool S is formed with recesses 5 adapted to receive pins whichmay be engaged by lifting cables, chains, or the like.

As previously stated, one object of the invention is to provide a moldand stool assembly which 55 will cause the metal of the ingot castin'the mold to 'cool and solidify much more rapidly at its bottom thanat its top. To this end I employ a very massive stool, i. e., massive orheavy as compared to the mold proper, the stool preferably having a massequal to at least the mass of, l the mold proper, and the stool mass mayeven be 100% or more the mass 'of the mold proper, the specific massratio required for optimum cooling conditions depending upon suchfactors as the design of the mold, the height of the mold 10 relative toits cross-sectional dimensions, and the ratio of the coeflicient of heatconductivity of the stool material to that of the mold material. Forexample, if cast iron is the material employed in the construction ofboth the mold and the II stool, it is desirable that the ratio of thestool mass to mold mass be relatively high, e. g., of

the order of 1. or higher.

It is possible to reduce this mass ratio consid erably by constructingthe stool of material having a higher coeflicient of heat conductivitythan the material of the mold walls. I prefer to con-' struct the stoolof copper or of an alloy of high copper content, since, as is'wellknown, copper has a coeilicient of heat conductivity about eight timesthat of cast iron, of which ingot molds almost universally are made. Inthe preferred embodiments shown in the drawing, the stool is of copperand the mold proper of cast iron. The commercial production of thousandsof tons of forging and tool steel ingots in mold and stool assemblies ofthis kind has resulted in much improved crystalline structure in theingot: metal.

In adapting the invention for commercial use it became necessary toprovide means for preventing the copper stool from being eroded or cutaway by the stream of molten metal entering the mold. Copper has amelting point about 600 F. lower than that of most carbon steels so thatthe stream of hot steel entering the mold 46,

under high velocity pressure has a strong tendency to melt and erode orcut away the copper stool. Copper is expensive, and furthermore, it

is undesirable to permit copper to be washed away from the stool andincorporated in the ingot metal, thereby disturbing the steel analysis.

To prevent this undesired cutting away of the stool I provide a coveringor. protective plate P which rests upon the stool and extends up intothe mold, the plate being so positioned as to receive the impact of theentering stream of molten steel, It is important that the plate P, whichis constructed of material such as ferrous material more resistant tothe cutting action of liquid steel than the copper stool, be as thin ascompatible with its necessary function of protecting the copper stool.By making the plate as thin as permitted by such considerations, it willhave only a minimum retarding effect upon the abstraction of heat fromthe ingot by the copper stool. The plate may be as thin as one-eighthinch, when used with a relatively small assembly, and should not exceedone inch in thickness, even with large assemblies. Preferably the weightof the plateshould be less than about 1% of the weight of the stool. Ihave found that by using thin plates of ferrous material the copperstool is given full protection without interfering to any noticeableextent with the rate of heat absorption from the bottom of the ingot.The plates preferably are so thin that they actually are melted, atleast partially, by the stream of molten steel so that they becomewelded to the bottom of the inset.

A further factor requiring consideration and treatment in order to adaptthe assembly for commercial use, is that of maintaining the jointbetween the mold and stool sealed, 1. e., safe against leakage or runouts. I have found that assem blies in which the protection plateoverlies the entire stool, or at least is large enough to extend underthe mold walls, (an arrangement not shown in the drawing) areunsatisfactory because of the leakage of metal between the bottom of themold and the protecting plate. Even if the leakage is only slight,resulting merely in the forma tion of a fin between the mold andprotecting plate, serious complications result. Such a fin. lying underthe bottom of the mold walls, interferes with the stripping of the ingotrelatively upward through the mold. A feature of my present inventionconsists in the provision of a novel arrangement of stool, protectingplate, and mold which effectively prevents the formation of even a smallfin under the mold walls. To this end the protecting plate P is made ofsuch size and shape as to extend up into themold matrix with itsmarginal edge 6 in close proximity to but slightly spaced from the innerlower portions of the mold walls, thereby providing a narrow channel I,the bottom of which is constituted by a substantially annular section ofthe copper stool. Molten steel which enters the channel I will contactthe copper stool and will chill very rapidly, rendering it practicallyimpossible for any steel to leak under the bottom of the mold walls. Thevolume of steel which can enter the channel and directly contact thestool is so small that the latter can not possibly be damaged. Moreover,the steel entering the channel is relatively quiet as compared to thehigh velocity stream which impinges upon the plate substantially at itscen- Since it is important that the channel 1 be reasonably uniform incross section, I prefer to provide means for centering the plate P onthe stool. In the form shown, the stool is formed with a recess 8 whichreceives a centering pin 8 integral with or connected to the stool.

Figure 3 shows a modified assembly which may be used when it is desiredthat the ingot have a generally tapered, or necked-in lower end. In thisform the parts are the same as those shown in Figures 1 and 2 with theexception that the plate P is dished as at l0 so as to fit into adepression II in the stool.

It will be understood that while the mold and stool assemblies shown anddescribed embody the invention in practical and the at present preferredforms, changes may be made without departing from the invention asdefined in the claims. 7.

I claim:

1. A mold and stool assembly comprising metallic walls defining avertically extending matrix having a bottom opening, a massive metallicstool upon which the mold is adapted to rest, the mold walls engagingthe stool immediately adjacent the mold bottom opening, and a relativelythin ferrous plate adapted to rest in close contact .with the upper faceof the stool and extending up into the mold bottom opening, said platebeing of slightly less cross sectional area than 1 the cross sectionalarea of the smallest part .of the mold bottom opening into which itextends, the periphery of said plate being spaced inwardly from theinnermost mutually contacting parts of the mold and stool.

2. A mold and stool assembly comprising ferrous walls defining avertically extending mold matrix having a bottom opening, a massivecopper stool upon which the mold is positioned, the mold walls engagingthe stool immediately ad- Jacent the mold bottom opening, and a ferrousplate adapted to rest upon and in close contact with the upper face ofthe stool and extending up into the mold bottom opening, said platebeing of slightly less cross sectional area than the cross sectionalarea ofthe smallest part of the mold bottom opening into which itextends, the periphery of said plate being spaced inwardly from theinnermost mutually contacting parts of the mold and stool. 3. A mold andstool assembly comprising walls constructed of ferrous material anddefining a vertically extending mold matrix having a bottom opening, astool upon which the mold is adapted to rest composed of coppermaterial, the mold walls engaging the stool immediately adJacent themold bottom opening, and an impact plate composed of ferrous materialseated upon and in close contact with the upper face of the stool, saidferrous plate being of slightly less cross sectional area than the crosssectional ,area of the smallest part of the mold bottom and extendingfrom the lower face of said mold bottom opening upward into saidopening, the periphery of said plate being spaced inwardly fromthe'innermost mutually contacting parts of the mold and stool, theweight of said stool being equal to at least 15% or more of the totalweight of the walls of the ingot mold, and the weight of said platebeing less than 1% of the weight of said stool.

4. An ingot mold and stool assembly comprising walls defining avertically extending mold matrix open at its top and bottom ends, amassive stool supporting said mold and being made of material having acoefilcient of heat conductivity several times that of the mold wallmaterial, and a thin metallic plate seated upon said stool and extendingupwardly into said mold matrix, said plate being constructed of materialmatrix, open at its top and bottom ends, a massive stool supporting saidmold and being made of material having'a coefiicient of heatconductivity several times that of the mold wall material, a thin'metallic plate seated upon said stool and extending upwardly into saidmold matrix, said plate being constructed of material more resistant tothe cutting action of liquid steel than said stool, and the size andshapeof said plate being such that its marginal edges extend aroundwithin in close proximity to but slightly spaced inwardly from theinnermost faces of the mold walls adjacent the point between the moldand the stool, thereby providing a narrow marginal sealing channelbetween the plate and mold walls, the bottom of said channel comprisinga portion of the upper face of the stool, and means for centering saidplate on said stool.

sive stool supporting said mold and being made of material having acoeflicient of heat conductivity several times that of the mold wallmaterial, and a thin metallic plate seated upon said stool and extendingupwardly into said mold matrix, said plate being constructed of materialmore resistant to the cutting action of liquid steel than said stool,and the size and shape of said plate being such that its marginal edgesextend around within 'in close proximity to but slightly spaced inwardlyfrom the inner faces of the mold walls adjacent the joint between themold and the stool, thereby providing a narrow marginal sealing channelbetween the plate and mold walls, the bottom. of said channel comprisinga portion of the upper face of the stool, said stool being formed witha. depression having-upwardly and outwardly taperedside walls and saidthin plate being dished to conform to the shape of saiddepression and tofit snugly therein.

EMIL GATHMANN.

